Line printer



y 7, 1964 .1. E. LJUNGBERG LINE PRINTER 2 Sheets-Sheet 1 Filed Nov. 1, 1962 INVENTOR JOHN ER LJUNGBEEG July 1964 J. E. LJUNGBERG 3,139,822

LINE PRINTER Filed Nov. 1, 1962 2 Sheets-Sheet 2 FIG. 4

INVENTOR.

JOHN EE/K LJUNGBERG A-r mm: m-

United States Patent 3,139,822 LINE PRINTER John Erik Ljungberg, Solna, Sweden, assignor to Aktiebolaget Atvidabergs Industrier, Atvidaberg, Sweden, a joint-stock company of Sweden Filed Nov. 1, 1962, Ser. No. 234,630 Claims priority, application Sweden Dec. 2, 1961 4 Claims. (Cl. 161-93) The present invention relates to a line printer in which a number of character types, one after the other, are set on a common line, where upon the whole line is printed at one time. The printer is especially adapted for print ing characters stored in serial electronic registers at the output of which each character is represented by a pulse train. The number of pulses contained in this train is determining the character to be printed.

A printer of this kind is previously known from US. Patent 3,106,889, but it is provided with an electromagnet at each character position, in addition to some electromagnets common to all character positions. A printer of this kind will therefore be very expensive nad complicated.

Another kind of printer is provided with one single character carrier which is displaced along the line on which the characters are to be printed as the characters are fed out from the register. In this case it is possible to save many components, but it is necessary to perform a separate printing stroke for each character, that is, a row will be printed comparatively slowly.

The present invention relates to a line printer which performs the printing operation of all the characters of a row at one time without requiring separate setting magnets for the different character positions.

A line printer with a plurality of type carriers according to the invention, particularly intended for printing characters stored in electronic registers, from which printing instructions are obtained as a plurality of pulse trains separated by space pulses, each pulse train representing a character on the line and containing a number of pulses corresponding to the position of the selected type on the type carrier is characterized by an indexing mechanism controlled by said pulse train and comprising a pawl member for each type carrier, and a selector mechanism controlled by said space pulses for forcing said pawl members, one after the other into engagement with a toothed portion of the pertaining type carrier for stepping the latter in pace with the following pulse train, whereupon the selector mechanism again moves the pawl member out of engagement at the same time as it is moving the next pawl member into engagement with the pertaining type carrier.

The invention is to be described closer with reference to the attached drawings of which FIG. 1 shows the mechanical construction of a printer according to the invention.

FIG. 1A is a perspective view of one of the type bars of the printer.

FIG. 2 schematically shows how the different cam discs of FIG. 1 are arranged.

FIG. 3 shows a part of a cam disc provided with a contact arrangement.

FIG. 4 shows in principle the electric circuits which can be used for controlling the printer.

The printer, as shown in FIG. 1, is mounted in a rack comprising two side plates 1 and 2 and two end plates of which only plate 3 is shown in the figure. It is provided with as many type carriers, consisting of type bars, as corresponds to the greatest number of character positions which may be located on one line, but in the figure only two type bars T and T are shown. Each type bar is provided with a type head 4 provided with all the 3,139,322 Patented July 7, 1964 ice characters which may be printed, for example the digits 0-9. FIG. 1A shows such digit characters on the face of the type head. The upper edge of each type bar is provided with teeth 5 having a pitch corresponding to the space between the types on the type head. The type bars are supported by two fixed studs 6 and 7 which are attached tothe side plates 1 and 2 and pass through slots 8 and 9 on all the type bars. The bars bars are slidably mounted in slits of a guide plate 10 and are normally kept in their right hand limit position by springs 11 which are arranged between a lip 12 on the type bars and a stud 13 fastened to the side plates.

A desired type bar is selected for operation by means of a selector mechanism comprising a stepping magnet 14, the armature 15 of which actuates a lever 16. The latter is pivoted on a bolt 17 fixed to the side plate 2. The lever is provided with a spring-loaded pawl 18, which, when the armature 15 is energized is turning the pinion 19 one tooth. The pinion 19 is fixed to a shaft 20 which is rotatably supported by the side plates 1 and 2. A number of cam discs K K located adjacent to the per taining type bars T T and an additional cam disc K, are also attached to the shaft 20. The cam discs Ii -K and K are each provided with grooves 21, and the grooves of the different discs are mutually displaced an angle corresponding to the pitch of the pinion 19. Said pinion is provided with the same number of teeth as the total number of cam discs K K K The cam discs K K each coact with a cam follower 22 shaped as a pawl. Said pawls are pivotal on a bar 23 and are by means of springs pressed against the pertaining cam disc. The pawls are provided with a projection 24 which when the pawl drops into the notch of the cam disc is brought into position for engaging the teeth 5 on the upper edge of the pertaining type bar.

The cam disc K coacts with a cam follower shaped as a stud 25 attached to a lever 26. The lever 26 and a similar lever 27 are rockably mounted on a shaft 28 and they support a bar 29 on which pawls 30 coacting with the type bars are pivoted. The pawls are spring loaded for engaging the teeth of the type bars and prevent the type bars from being retracted toward the right by the springs 11 as long as the cam follower 25 is resting against the unbroken periphery of the cam disc K As soon as the cam follower drops into the notch 21 the bar 29 is lifted causing all the pawls 30 to be released from the engagement with the teeth 5 and enabling all the type bars to returnto their initial position.

The desired type on the type bars is selected with the aid of an indexing mechanism comprising a stepping magnet 31 the armature 32 of which is attached to two levers 33, 34 the upper part of which carries the bar 23 mentioned above. The levers are pivotal about a shaft 33'. When the magnet 31 is energized, all the pawls 22 are moved forwards one type space, but only the pawl which has dropped into the notch of the pertaining cam disc will come into contact with the type bar and move it forward one type pitch. The other cam followers slide along the periphery of the cam discs and cannot engage the type bars. In FIG. 1 the cam follower pertaining to the type arm T is in the position for moving the type bar.

After the type bar has been stepped the desired number of steps, the magnet 14 is energized by a pulse causing the shaft 20 and thus the cam discs T --T to be turned by one pitch of the pinion 19. The next pawl in the row then drops into the notch 21 of the pertaining cam disc and engages the type bar while the pawl operative before is again lifted against the periphery of the cam disc. When the last type bar has been set into the printing position the magnet 35 is energized and its armature 36 is attracted pressing the pressure roller 37 against'the type bars T T in a printing stroke. The paper and the carbon ribbon are guided between the print ing roller and the heads in a conventional manner.

During the next stepping of the pinion 19 the cam follower will drop into the notch 21 of the cam disc K causing the levers 26, 27 and the bar 29 mounted between them to be rocked around the shaft 28. The pawls 30 are released from the engagement with the teeth of the type bars and the type bars return to their initial position under the action of the springs 11. The printer is now ready for a new operation.

The circuits required for controlling the operation of the printer are shown in FIG. 4. Here designates an electronic register, for example a decimal register of a computer. The register is of the shift register type that is, all the characters are shifted one step upwards when a shift pulse is applied to the shift input 41. During each shift operation the character located in the upper position is obtained on the output 42 and is fed to the corresponding position of a counter 43.

The print operation is started by applying a starting pulse to the input 44, for example manually. The pulse passes the OR-gate 45 and is triggering a monostable flip-flop 46. The output pulse is transferred Via the OR- circuit 47 to the input of a pulse generator 48 which will start and generate a pulse for the selector magnet 14, causing the pinion 19 to be stepped one step. Supposing that the shaft 20 had such a position that the cam follower 25 was located down in the notch 21 the shaft will be turned to the position where the pawl 24 can drop into the notch 21, on the cam disc K The output pulse of the flip-flop 46 also sets a bistable flipflop 49 generating a condition for opening the AND- gate 50, and in addition it causes the intelligence storage of the register 40 to be shifted one step upwards. The digit, for example 7, located in the highest position of the register is transferred to the counter 43. The monostable flip-flop 46 returns to its initial state after a time which is sufficient to allow the pawl 24 of the disc K to drop to the bottom of the notch 21 Now the AND-gate 50 receives a further condition for opening and it will pass stepping pulses PG from a pulse source. Said pulses trigger the pulse generator 56 feeding the magnet 32 with stepping pulses in pace with the pulse train PG simultaneously as the counter is stepped backwards, in this case seven steps.

When the counter is zero set by the seventh pulse PG a pulse is obtained for zero setting the flip-flop 49 causing the passage of pulses through the AND-gate 50 to be interrupted. In addition a pulse is obtained from the flip-flop which is transferred to the flip-flop 46 through the contacts 51 and 52 and the OR-gate 45. When said flip-flop is triggered the cycle described above is repeated, causing the second cam disc K (not shown) to be turned to the active position at the same time as the second digit of the register 40 is transferred to the counter 43. The second type bar T is then set into the desired position in the manner described above. The other type bars are then set one after the other. When the cam discs are turned to the position where the pawl of the last type bar drops into the notch 21 of the cam disc T, the change-over contact 51, 52, 53 arranged at the cam disc K. is actuated by a nose 54 (FIG. 3), causing the contact 51, 52 to be interrupted while the contact 51, 53 is closed. The pulse generated when the flip-flop 49 is set to zero activates the pulse genera- .tor 55 which delivers a current pulse to the print magnet 35, and the pressure roller 37 strikes the paper and the carbon ribbon against the type heads. At the end of the print pulse a pulse is generated which is fed to the pulse generator 48 through the OR-gate 47. The magnet 14 now steps the pinion 19 a further step causing the cam follower 25 to drop into the notch 21 and to release the type bars. A complete line is now printed and the printer can perform a new print operation after a new number has been set in the register.

The invention is of course not limited to the embodiment described. It is for example possible to shape the type carriers as type wheels instead of as type bars. In this case the type wheels can either be driven by toothed bars replacing the type bars or the type Wheels may be rotatably supported by the shaft 20. In the latter case each type wheel is provided with'a toothed portion which is directly engaged by the pawls 22.

I claim:

1. A line printer for line-printing bits of intelligence stored in an electronic register including circuit means for generating successive indexing pulse trains, each being indicative of a bit of intelligence to be printed in a line and circuit means for generating between each two indexing pulse trains a selecting pulse indicative of the positions of the bits of intelligence in the line, said line printer comprising a plurality of lengthwise displaceable intelligence carriers, each carrying a row of bits of intelligence to be printed and each having a toothed portion, selecting means to select a carrier to be displaced, and bit-indexing means to select for printing one of the bits on the carrier selected by the carrier-selecting means, said carrier selecting means comprising a plurality of cam discs each associated with one carrier and each having an indexing notch, the indexing notches in the cam discs being staggered in reference to each other, a common shaft mounting said cam discs for rotation in unison with the shaft, and disc stepping means coacting with said shaft, said disc stepping means being controlled by said selecting pulses and controlling said shaft to rotate the same through one step in response to each selecting pulse to place the indexing notch of a selected cam disc in a predetermined angular position, and said indexing means including a plurality of movable cam followers, one for each cam disc and intelligence carrier, each of said cam followers having a pawl simultaneously engaging the teeth of the respective intelligence carrier and the indexing notch of the associated cam disc when the indexing notch is rotated into said predetermined angular position by said disc stepping means, and carrier stepping means controlled by the indexing pulses and controlling said cam followers to actuate the same in accordance with the number of pulses in a pulse train to displace the respective carrier from an inactive position to a position corresponding to said number, thereby placing a selected bit of intelligence on a selected intelligence carrier in position for printing.

2. A line printer according to claim 1 wherein each intelligence carrier and the associated cam disc are disposed side by side in parallel planes, and wherein the pawl of each movable cam follower is riding along the periphery of the respective cam disc as the same is rotated and has a portion overlying the toothed portion of the respective intelligence carrier, said overlying pawl portion being clear of said toothed portion when the pawl engages the unnotched portion of the periphery and engages the toothed portion when the pawl portion engages the indexing notch.

3. A line printer according to claim 1 and comprising spring means coacting with said intelligence carrier to bias the same into its inactive position, releasable locking means retaining the displaced intelligence carrier in the printing position against the action of said spring means, electrically operated release means for releasing said locking means, and release circuit means for energizing said release means.

4. A line printer according to claim 3 wherein said releasable locking means comprise a further cam disc mounted on said common shaft for rotation in unison therewith and having in its periphery a release control notch, a movable cam follower engageable with said control notch in a predetermined angular position of said further cam disc, a movable control pawl for each into an angular position in which the notch therein is engaged by the cam follower of the locking means, said drive means being energizable by said release circuit means.

References Cited in the file of this patent UNITED STATES PATENTS 2,297,803 Scheerer Oct. 6, 1942 2,323,825 Maschmeyer July 6, 1943 2,720,832 Luning Oct. 18, 1955 2,910,935 Cignetti Nov. 3, 1959 

1. A LINE PRINTER FOR LINE-PRINTING BITS OF INTELLIGENCE STORED IN AN ELECTRONIC REGISTER INCLUDING CIRCUIT MEANS FOR GENERATING SUCCESSIVE INDEXING PULSE TRAINS, EACH BEING INDICATIVE OF A BIT OF INTELLIGENCE TO BE PRINTED IN A LINE AND CIRCUIT MEANS FOR GENERATING BETWEEN EACH TWO INDEXING PULSE TRAINS A SELECTING PULSE INDICATIVE OF THE POSITIONS OF THE BITS OF INTELLIGENCE IN THE LINE, SAID LINE PRINTER COMPRISING A PLURALITY OF LENGTHWISE DISPLACEABLE INTELLIGENCE CARRIERS, EACH CARRYING A ROW OF BITS OF INTELLIGENCE TO BE PRINTED AND EACH HAVING A TOOTHED PORTION, SELECTING MEANS TO SELECT A CARRIER TO BE DISPLACED, AND BIT-INDEXING MEANS TO SELECT FOR PRINTING ONE OF THE BITS ON THE CARRIER SELECTED BY THE CARRIER-SELECTING MEANS, SAID CARRIER SELECTING MEANS COMPRISING A PLURALITY OF CAM DISCS EACH ASSOCIATED WITH ONE CARRIER AND EACH HAVING AN INDEXING NOTCH, THE INDEXING NOTCHES IN THE CAM DISCS BEING STAGGERED IN REFERENCE TO EACH OTHER, A COMMON SHAFT MOUNTING SAID CAM DISCS FOR ROTATION IN UNISON WITH THE SHAFT, AND DISC STEPPING MEANS COACTING WITH SAID SHAFT, SAID DISC STEPPING MEANS BEING CONTROLLED BY 